Synthetic resin containers made from a synthetic resin such as polyester or polyethylene terephthalate (PET) have been widely put into practical use as containers for beverages. A preform that is to be formed into a synthetic resin container by blow-forming can be integrally formed by compression-molding by using a compression-molding machine. In executing the compression-molding, the synthetic resin in a molten state is extruded from an ejection port of a die head of an extruder and is fed to the compression-molding machine by a resin feeder.
The extruder heats and melts a resin material and continuously extrudes the molten resin from the die head. The molten resin generates acetaldehydes or oligomers depending upon the heating temperature. The acetaldehydes or oligomers deposited on a PET bottle adversely affect the taste. Therefore, the extruder extrudes the molten resin at a low temperature to suppress the generation of acetaldehydes or oligomers.
Even if the molten resin is extruded at a low temperature, however, acetaldehydes or oligomers generate in the form of a vapor in trace amounts and deposit on the holding unit upon coming in contact therewith. Further, the molten resin itself (e.g., resin scum, etc.) may often adhere and deposit.
Patent document 1: WO2005/102641